Test pilot Joe Walker was killed June 8, 1966, when his F-104 chase plane collided in midair with an XB-70 supersonic bomber during a formation flight for a publicity photo. The catastrophic accident took the life of the top NASA test pilot, who earned astronaut wings by piloting the X-15 into space three times, as well as that of Air Force Maj. Carl Cross, one of two pilots of the XB-70. Thursday, on the 40th anniversary of that fateful flight, Walker's son and other admirers visited the crash site in a remote portion of the Mojave Desert to pay their...